Library not being located with directory set in LD_LIBRARY_PATH

Question

I am attempting to verify the installation of CUDA and am running into some issues. I have successfully built all of the examples that come with the GPU computing SDK. When I try to run deviceQuery however, I get an error saying that libcudart.so.4 can not be found.

However:

echo $LD_LIBRARY_PATH

returns

/usr/local/cuda/lib64

Inside of that directory is a file:

libcudart.so.4

What other sort of errors could be causing the library to not be located?

EDIT for Fran's answer:

1. Yes, I am exporting the variable
2. I am not sure if the program is 64-bit, however it came as part of a 64-bit SDK install, so I would like to assume it is

3. Output of ldd:

   #ldd deviceQuery
   linux-vdso.so.1 =>  (0x00007fff94ecc000)
   libcudart.so.4 => /usr/local/cuda/lib64/libcudart.so.4 (0x00007f2d4658a000)
   libcuda.so.1 => /usr/lib64/libcuda.so.1 (0x00007f2d45b1e000)
   libstdc++.so.6 => /usr/lib64/libstdc++.so.6 (0x00000037f1200000)
   libm.so.6 => /lib64/libm.so.6 (0x00000037e5e00000)
   libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00000037f0600000)
   libc.so.6 => /lib64/libc.so.6 (0x00000037e5600000)
   libpthread.so.0 => /lib64/libpthread.so.0 (0x00000037e5a00000)
   libdl.so.2 => /lib64/libdl.so.2 (0x00000037e5200000)
   librt.so.1 => /lib64/librt.so.1 (0x00000037e6200000)
   libz.so.1 => /lib64/libz.so.1 (0x00000037e6e00000)
   /lib64/ld-linux-x86-64.so.2 (0x00000037e4e00000)
   

I have found that I can run it as a normal user, but doing so causes it to fail since the user does not have access to the GPU. Running it with sudo causes the missing file error.

Running:

sudo ldd deviceQuery

confirms the missing libcudart.so.4 on the second line of the output.

Answer 1

1. Did you export LD_LIBRARY_PATH from the shell in which you are running the program?

2. Are both the program and shared library 64-bit binaries (or both 32-bit binaries)?

3. What is the output of ldd program, where program is the program that can't find the library at runtime?

Answer 2

If you are building from source, you have the option to build it such that it uses an existing library path via --prefix= or --libdir=. Otherwise you can:

• add /usr/local/cuda/lib64 to the LD_LIBRARY_PATH in /etc/profile
• move it manually (to /usr/local/ for example) and make a symlink for /usr/local/cuda to /usr/local
• use LDPRELOAD to preload the missing libs manually

Just a quick reminder on LD_LIBRARY_PATH - keep in mind that the more paths you add, the more the dynamic linker has to look through to find it.